Purification of barium



May 8 1945- P. P. ALEXANDER PURIFICATION OF BARIUM Original Filed March 5, 1943 INVENTOR Pfff/E /f AME/v1 MDE/e EY @M n@ ATTORNEYS Patented May i4 their rra PURWIICTIN @1F BARKEIM Original application March 5, 1943, Serial No., 478,095. Divided and this application reprit be, 1944, Serial N0. 532,736

Clas.

This invention relates to the purification of barium contaminated with metal impurities havlng a lower boiling point, and has for its object more particularly certain improvements in the method of purifying barium contaminated with alkali metal impurities, such as sodium and potassium.

Barium metal is usually made by subjecting fused barium chloride to electrolysis. Since the salts of the alkali metals, sodium and potassium, are usually present in the barium chloride, the resulting barium metal is usually contaminated with a small amount of alkali metal, as well as of the barium chloride itself. To purify the barium metal, 1t has been proposed to subject it to distillation in a closed retort that has been evacuated to remove objectionable air. The distilled barium is permitted to condense in a cooler part of the retort, usually in the form of a more or less spongy deposit; while the alkali metal impurities condense in a still cooler part of the retort. After cooling the retort, air is admitted, the retort is opened and the condensed barium is removed. The resulting product is so reactive that it frequently oxidizes rapidly on the surface and produces heat in sulcient amount to ignite the whole mass, with the result that fires are quite common. This objectionable result is Ci. 'i5-437) These and other features oi the invention may be better understood by referring to the accomiii panying drawing, taken in conjunction with the following description, in which:

Fig. l is a diagrammatic representation, being a side elevation in section, of an apparatus with which the method of the invention may be prac ticed; and

Fig. 2 is a horizontal section on the line 2-2 of Fig. l.

The apparatus shown comprises an outer retort i@ supported within a heating furnace la, the retort being held in position by means of two or more supports i2 resting on top of the heating furnace. The retort preferably consists of heatresistant steel. It is provided with a removable cover i3 having attached thereto a vertical pipe It and lateral valved branches i5 and l, connectible with a source or vacuum, and air, reu spectively. A removable inner retort gli, having an kopen top, rests within the outer retort. .a removable tray 2l rests over the open top of the retort, being supported thereon by means or three or more lugs 22 extending over the wall of the 25 inner retort. The heating furnace ii consists esall the more apt to occur because of the presence of the more highly reactive sodium and potassium. The small deposits of sodium and potassium are so reactive that they almost invariably catch re when the retort is opened and they come in contact with the oxygen of air.

As a result of my investigations, I have discovered that these disadvantages may be overcome for the most part. The alkali metals, sodium and potassium, may be segregated from the barium metal in a form to make them non-iniiammable on exposure to the oxidizing influence of air. The barium metal may be separately collected and it may at the same time be substantially freed of its chloride.

In accordance with the invention, the barium metal is heated in the absence of air to a temperature suiciently high to distill the alkali metal impurity or impurities. The alkali metal vapor is selectively oxidized by bringing it in reactive contact with a refractory oxide, such as titanium oxide, zirconium oxide and chromium oxide, and the resulting oxidized alkali metal impurity is collected as a solid separate from the barium metal to be puried. The barium metal itself is advantageously distilled and condensed separate from the oxidized alkali metal impurities.

sentially of a rectangular chamber 23 having a refractory bottom Zt, side and end walls 5.125, and

a top 2t having an opening of a size adapted to receive the outer retort. in expanding ope 2i is provided at or near a lower corner of one of the side walls of the chamber, for the introduction of heating gases into the chamber. .a similar opening 2d is preferably provided at or near an opposite corner, as a spare or auxiliary means for introducing heating, orcoolins, eases into the chamber. When not in use, the opening 28 is closed. A flue opening 2@ extends through the same wall as the opening 2l, preferably atv a higher level, so that heating gases passed into the chamber through the opening 2l tend to pass around the retort before leaving the chamber through the ue opening 29.

The apparatus may be used as follows: A charge of barium, for example. contaminated with sodium, potassium, and barium chloride, is placed in the bottom of the inner retort 2t. The inner retort is then placed in the outer retort id. A layer of titanium oxide 'ad is placed in the tray 2i l, which is in turn placed across the open top oi the inner' retort. The removable cover i3 is placed on the outer retort i@ and locked thereon to provide a sealed joint. The lateral branch it is then connected to a source of vacuum. With the valve oi this lateral branch open, and the valve ci the other lateral branch it closed, the

outer and inner retorts are placed under vacuum to remove objectionable air.

Heating gases are passed through opening 2l into the heating chamben, Where they circulate almost completely around the retort and then pass through lthe iiue opening 29 to the outside atmosphere. As the lower portion of the outer retort i is heated, the lower portion of the inner retort 20 is also heated. As the temperature rises, a point is reached Where the sodium and potassium present in the barium are distilled. The resulting sodium and potassium vapors rise to the upper and cooler portion of the retort where they come in contact with the titanium oxide 30 in the tray 2i. Due to their aliinty for oxygen, the sodium and potassium are promptly oxidized and the titanium dioxide is reduced to titanium and a sub-oxide or titanium, according to reactions which may be indicated as follows:

As the temperature at the bottom of the inner retort continues to rise, a point is reached where the barium is distilled and its resulting vapor tends to condense and settle out against the wall oi the inner retort immediately below the tray i6. Some barium vapor may of course rise sufficiently to come in contact with titanium dioxide in the tray and reactl with it in a manner similar to sodium or potassium vapor. The bulk of the distilled barium may, however, be separately condensed and collected, as shown. A residue consisting essentially of barium chloride, admixed perhaps with a small amount of sodium chloride or potassium chloride, or both, remains as a residue in the bottom of the inner retort.

The introduction of heating gases to the heating chamber is stopped and the retort is permitted to cool. The cooling operation maybe accelerated by passing cooling air through the heating chamber, for example, through the opening 28, or by removing the outer retort and its contents from the heating chamber. After the retort has been suitably cooled, lateral branch i6 is opened to admit air to the interior of the retorts, after which the cover i3 is removed. The inner retort and tray are pulled out of the outer retort; the tray is removed, and the condensed barium is scraped off and separately recovered. The residues are advantageously removed by washing the inner retort with water.

It will be clear to those skilled in this art that theinvention lends itself to numerous modications. Instead of titanium oxide, other suitable refractory metallic oxides, such as zirconium oxide and chromium oxide, may be employed, either separately or admixed.

In the practice of the invention, advantage is taken of the relative boiling points of the metals. The boiling points of sodium and potassium are substantially below that of barium. The temperature of the barium is, therefore, gradually elevated to a point where the alkali metal impurity of lower boiling point is distilled. By heating its bottom, the retort is caused tov yield a graduated temperature range, being hottest at its bottom and coolest at its top, Since the sodium and potassium have the lower boiling points, their vapors tend selectively to rise highest in the retort. Since the barium has the higher boiling point, its vapor tends not to rise as high in the retort. The barium vapor meets a temperature environment conducive to condensation. In other words, the barium metal may be made to condense in an intermediate section of the retort where the temperature is high enough to keep the alkali metal vapors in vapor form. The alkali metal vapors, on the other hand, tend to rise to a cooler portion of the retort, where they were heretofore condensed, but where they are now converted into harmless compounds in accordance with the present invention.

This application is a division of my co-pending application Serial No. 478,095, filed March 5, 1943. i

I claim:

1. In the method of purifying barium contaminated with an alkali metal impurity, the improvement which comprises heating the barium in the absence of air to a temperature at which the alkali metal impurity but not the barium is distilled, selectively oxidizing the resulting alkali metal impurity vapor in a zone removed from the main body of barium to be puriiied, and collecting the oxidized alkali metal impurity as a solid separate from the barium to be purified.

2. Method according to claim l, in which the resulting vapor of the alkali metal impurity is selectively oxidized by bringing it into reactive contact with a refractory metal oxide in a zone removed from the main body of barium to be purified.

3. Method according to claim 1, in which the resulting vapor of the alkali metal impurity is selectively oxidized by bringing it into reactive contact with titanium oxide in a zone removed from the main body of barium to be purified.

4. M'ethod according to claim l, in which the resulting vapor of the alkali metal impuritl `1is selectively oxidized by bringing it into reactive contact with zirconium oxide in a zone removed from the main body of barium to be purified,

5. Method according to claim 1, in which the resulting `vapor of the alkali metal impurity is selectively oxidized by bringing it into reactive .contact with chromium oxide in a zone removed from the main body of barium to be purified.

6. Method according to claim 1, in which the barium to be puried is also distilled, and condensing the resultingbarium vapor as a solid separate from the oxidized alkali metal impurity in a zone intermediate that in which the alkali metal impurity is oxidized and that from which the main body of barium is distilled. l

'7. In the method of purifying barium contaminated with sodium as an impurity, the improvement which comprises heating the' barium in the absence of air to a temperature sufficiently high to distill the sodium but not the barium, selectively oxidizing the resulting sodium vapor in a l zone removed from the main body of barium to barium to be puried.

10. Method according to claim 7, in which the resulting sodium vapor is selectively oxidized by 11. Method according toclaim 7, in which th resulting sodium vapor is selectively oxidized by bringing it into reactive contact with chromium .oxide in a zone removed from the main body of barium to be puried.

12. Method according to claim 7, in which the barium t-o be puried is also distilled, and condensing the resulting bariurnvapor as a solid separate from the oxidized sodium impurity in a zone intermediate that in which the sodium impurity is oxidized and that from which the main body of barium is distilled,

13. In the method of purifying barium contaminated with potassium as an impurity, the improvement which comprises heating the barium in the absence of air to a temperature sufficiently high to distill the potassium but not the barium, selectively oxidizing the resulting potassium vapor in a zone removed from the main body of barium to be purified, and collecting the oxidized potassium as a solid separate from the resulting potassium vapbr is selectively oxidized by bringing it into reactive contact with zirconium oxide in a zone removed from the main body of barium to be puried.

17. Method according to claim 13, in which the resulting potassium vapor is selectively oxidized by bringing it into reactive contact with chromium oxide in a zone removed from the main body of barium to be puried.

18. Method according to claim 13, in which the barium to be purified is also distilled, and condensing the resulting barium vapor as a. solid separate fromA the oxidized potassium impurity in a zone intermediate that in which the potassium impurity is oxidized and that from which the main body of barium is distilled.

19. In the method of purifying barium contaminated with an alkali metal impurity, the improvement which comprises heating the barium in`the absence of air to a temperature at which the alkali metal impurity but not the barium is distilled, selectively oxidizing the resulting alkali metal impurity vapor by bringing it into reactive contact with a refractory metal oxide in a zone removed from the main body of barium to be puried, and collecting the oxidized alkali metal y impurity as a solid separate from the barium to be purified.

20. In the method of purifying barium 'contaminated with sodium as an impurity, the improvement which comprises heating the barium in the absence of air to a temperaturesufficiently high to distill the sodium but not the barium, selectively oxidizing the resulting sodium vapor by bringing it into reactive contact with a refractory metal oxide in a zone removed from the main body of barium to be purified, collecting the oxidized sodium as a solid separate from the barium, distilling the barium, and condensing the resulting barium vapor as a solid separate'from the oxidized sodium impurity in a zone intermediate that in which the sodium impurity is oxidized and that from which the main body of barium is distilled.

PETER P. ALEXANDER. 

